<html>
<script>
    function run() {
        document.body.classList.toggle('noscroll');
        document.getElementById('spacer').style.height = '100%';
        // Scroll to the very end, including any fractional pixels
        document.body.scrollTop = document.body.scrollTopMax + 1;
    }
</script>
<style>
    html, body {
        margin: 0;
        padding: 0;
        background-color: green;
    }

    .noscroll {
        overflow: hidden;
        height: 100%;
    }
</style>
<body onload="run()">
 <div id="spacer" style="height: 5000px">
  This is the top of the page.
 </div>
 This is the bottom of the page.
</body>
